Pneumatically inflated tourniquets are known to those skilled in the art as evidenced by the U.S. Pat. Nos. 2,511,269; to Jones, 1,366,121; to Dorsey, 1,679,978; to Konwiser, et al 1,827,241; to Kempf, 3,086,529; to Munz, et al 2,031,870; to Vertuno, 2,045,750; to Buschenfeldt, 3,654,931; to Hazelwood, 3,906,937; to Aronson 4,210,147; to Nestor, et al 4,106,499; to Ueda 3,633,567; to Sarnoff and 3,120,846 to Fletcher. In each of these U. S. Patents, an inflatable tourniquet is wrapped about the limb and subsequently fastened, after which pneumatic pressure is forced into a bladder or chamber contained within the tourniquet.
U.S. Pat. No. 1,269,620 to Levine provides a tourniquet which can be slipped over one's limb. The tourniquet is an endless tubing having a lateral passageway connected thereto for increasing the internal pressure of the tubing.
U.S. Pat. No. 4,228,792 to Rhys-Davies proposes a fluid filled envelop in the form of a double wall tube of elastomer wherein the inner and outer walls are maintained below a threshold pressure. The cylindrical member can be secured on one's limb and is employed for forcing blood from a patient's limb.
It is possible to make an elastomeric toroidal member of a size to be received about one's finger, arm, or leg, wherein the thickness of the elastomeric wall of the toroid is selected along with the modulus of elasticity whereby continued inflation of the interior of the toroid will exceed a threshold value, whereupon further inflation will expand the toroid walls without a proportional increase in the interior pressure of the toroid.
It is desirable to have made available a tourniquet which can be placed about the extremity of a person's anatomy, such as a person's limb, by simply forcing the tourniquet into place at the desired location on the person's body. It would be desirable that such a tourniquet be previously inflated to the required internal pressure which precludes loss of blood from an injury associated with the limb. A tourniquet device which achieves these desirable goals is the subject of the present invention.
The elastomer of the novel tourniquet disclosed herein can be obtained from natural sources or synthesized artificially. The elastomer preferably is compounded and made into a selected thickness to impart the desirable properties of extensibility, stretchability, and toughness. Modulus is normally a function of the state of cure or degree of vulcanization, and is considered more important than tensile strength. As used herein the term "modulus of elasticity" is intended to mean the measure of stretch or elongation exhibited by the rubber as the chamber of the tourniquet is inflated; and, the term "threshold pressure" means the psi which must be effected on the internal wall surface that forms the tourniquet chamber in order that the volume of the chamber commences expanding at substantially constant internal pressure.
For example, a rubber balloon is difficult to inflate as a first volume of air is introduced into the chamber thereof; however, as the volume is increased an internal pressure is reached wherein further increase in volume is achieved without any further increase in the pressure, or at least, the increase in pressure required to achieve the additional volume is not proportional to the first increase in pressure required to achieve the first increase in volume.